Process for improving liquid fuels by treating with propanol and a metal passivator



United States Patent '0 PROCESS FOR IMPROVING LIQUID FUELS BY TREATINGWITH PROPANOL AND A NIETAL PASSIVATOR John E. Hickok, New ProvidenceTownship, Union County, George S. Tobias, Plainfield, and Robert V. J.McGee, Union, N. 1., assignors to Esso Research and Engineering Company,a corporation of Delaware Application November 15, 1951, Serial No.256,534

4 Claims. (Cl. 196-44) The present invention is concerned with a processfor producing liquid petroleum fuels of high quality. The invention ismore particularly concerned with a process for manufacturing gasolines,heating oils and other distillate fuels of high quality. Such fuels aremixtures of hydrocarbons and are used in internal combustion engines,like those with Otto or with Diesel cycle, in turbo-jet engines inaviation, and in various burner systems for domestic or industrialheating.

In accordance with the present invention, these fuels are treated withan alcohol, either alone or in conjunction with a metal-passivator, in amanner to produce improved fuels, stable against the formation ofsediment, sludge, gum or similar products of deterioration. Ametalpassivator is a salt that has the property of protecting ferrousmetals from corrosion.

It is well known in the art to make fuels from petroleum feed-stocks byvarious refining operations, including straight distillation from crudeoil and thermal or catalytic cracking. It is also well known in the artto treat distillate fuels, such as gasoline or heating oil, by variousprocesses in order to remove sediment or sediment-forming impurities andthus to improve the quality and stability of the products. Examples oftreating processes are acidtreating, caustic-washing anddoctor-sweetening. In certain instances, further improvement in qualityand stability has been achieved by the use of addition agents, forexample wti-oxidants and detergents in the fuels.

However, the conventional refining and treating processes, particularlywhen applied to fuels consisting wholly or in part of crackeddistillates, are not always completely adequate to prevent the formationof sediment during storage and use of the fuels. As a result, such fuelsmay form deposits when used in an engine or may cause clogging offilters, screens, orifices or conduits associated with the burnersystems in which they are used.

It has now been discovered that improved fuels, particularly gasoline,turbo-jet fuel, kerosene, heating oil and diesel fuel, may be obtainedby treating distillates with an alcohol and a metal-passivating saltsolution. The invention is preferably applied to distillates containingor more of stocks derived from thermal or catalytic cracking operations,having a vapor pressure below 13 pounds per square inch at 100 F., andboiling below 750 F. at atmospheric pressure. Examples of suchdistillates are aviation gasoline with about 7 pounds vapor pressure andabout 320 F. final boiling point, motor gasoline with about 8 to 12pounds vapor pressure and about 420 F. final boiling point, turbo-jetfuel with about 2 lbs. vapor pressure and 550 F. final boiling point,diesel fuels falling within ASTM specification D-975-48T (grades No. lDto 4-D inclusive) and fuel oils falling within ASTM specificationD39648T (grades No. l to 6).

As pointed out heretofore, the invention broadly is concerned with theproduction of high quality distillate products utilizing an alcoholalone or in conjunction with a solution of a metal-passivating salt.Various alcohols may be used, as for example, primary aliphatic alcoholshaving from one to five carbon atoms in the molecule, secondaryaliphatic alcohols having from 3 to 5 carbon atoms in the molecule,tertiary aliphatic alcohols having 4 to 5 carbon atoms in the molecule,cyclic alcohols like cyclo-hexanol, phenols like catechol, hetero-cyclicalcohols like furfuryl or tetrahydrofurfuryl alcohol, unsaturatedalcohols like vinyl or allyl alcohol, di-hydroxy alcohols like ethyleneglycol or propylene glycol or butane diol, and poly-hydroxy alcoholslike glycerol, etc. The aliphatic alcohols having up to 5 carbon atomsin the molecule are preferred and isopropanol is particularly preferred.

The amount of alcohol used may vary appreciably, as for example in therange from about 0.5% to 20% by volume based upon the amount of oilbeing treated. The preferred amount is in the range of about 1% to 5% byvolume. The treating temperature may range from 60 F. in open vessels to450 F. in closed systems. In general the effectiveness of the treatmentincreases with increasing temperature, However, a particularlyconvenient range of operating temperatures is between F. and 212 F.;while an operating temperature of from about F. to a temperature at orslightly above the normal boiling point, 181 F, of isopropanol isparticularly convenient for that reagent.

The metal-passivating salts are salts of sodium, potassium, ammonium ororganic amines with certain inorganic or organic acids. Generally, thesodium salts are preferred for reasons of convenience, economy andeffectiveness; but ammonium salts may be used for products in which thepossibility of entraining ash-forming constituents is desirably to beavoided; and amine salts may be used advantageously when enhancedoil-solubility of the reagent is desirable. The acidic component of thesalt is selected from the group, chromate, bichromate, phosphate,phosphite, nitrate, nitrite, borate and benzoate. Amine nitrites likemorpholine nitrite or diisopropyl amine nitrite are desirable for beingashless and being capable of sublimation. Sodium benzoate also sublimes.Sodium chromate or bichromate is convenient to be used in treatinggasoline but is less desirable for treating diesel fuels. Sodiumphosphate is particuiarly effective for imparting both antioxidant andrust-preventive effects. Sodium nitrite is the preferred reagent for usein conjunction with isopropanol in the treating of a wide variety offuels.

The process of the present invention may be more fully understood byreference to the drawings illustrating embodiments of the invention.Figure 1 illustrates an operation wherein a distillate is treated in afirst stage with an alcohol and the alcohol is removed in a secondstage. Figure 2 illustrates an operation wherein a distillate is treatedoptionally with a metal salt, which may conveniently be in the form ofan aqueous solution, in a first stage and is treated with an alcohol ina second stage and is separated from the alcohol in a third stage.

Referring specifically to Fi ure l, a distillate, which for the purposeof illustration is taken to be a heating oil containing more than 10% ofcracked gas oil, is introduced into a first treating zone 1 by means ofline 2 and is treated with an alcohol, for example isopropanol,introduced through line 3. The treated distillate and the alcohol areremoved from zone 1 by means of line 4 and introduced into a secondtreating zone 5 wherein the alcohol is removed from the treateddistillate through line 8 either by a stripping distillation or byselective extraction with a solution of metal-passivating salt, forexample sodium nitrite, which is introduced through line 7 if desired.The treated distillate is removed from zone 5 by means of line 6 andfurther refined or handled as desired.

Referring again to Figure 1, in an alternate operation,

the feed stock is a wide-cut distillate containing fractions of gasolineor turbo-jet fuel components as well as gas oil fractions, for example acatalytically cracked distillate boiling from about 100 F. to 650 F. Thedistillate. is treated with an alcohol boining below 400 F. in zone 1and is fractionally distilled in zone 5 so as to withdraw a treatedgas-oil as a residual fraction by means of line 6 and to recover atreated gasoline and/ or turbojet fuel, containing at least a portion ofthe alcohol in unreacted condition, as an overhead fraction by means ofline 8. A small amount of a preferably sublimable metal-passivator isintroduced through line 7 if desired. The gas oil is thus stabilizedagainst sediment formation and the overhead fraction is stabilizedagainst formation of either gum from oxidation in hot Weather or icefrom moisture contamination in cold weather.

Referring specifically to Figure 2, a distillate feed stock as describedfor Figure 1 is introduced into a first treating zone 10 by means ofline 11. In zone 10, according to one embodiment of the invention, thefeed stock is treated with a solution of metal-passivating salt, likesodium nitrite, introduced by means of line 12 and withdrawn b means ofline 13; but if, as hereinafter mentioned, a treatment withmetal-pas'sivating salt is selected as the alternative treatment in athird treating zone, the treatment in zone it can economically beomitted; and the process then becomes the same as in Figure 1. From zone10 the distillate is passed through line 14 to a second treating zone 15wherein the distillate is treated with an alcohol introduced by means ofline 16. The mixture of treated distillate and alcohol is transferredfrom zone 15 by means of line 17 to a third treating zone 18 wherein themixture is so treated as to remove the alcohol from the treateddistillate fuel. The treated fuel is removed from zone 18 by means ofline 19 and handled as desired.

One method of treating in zone 18 is to remove the alcohol by fractionaldistillation, which is particularly effective when there is aconsiderable difference in boiling points between the alcohol and thetreated fuel. The preferred method of treating in zone 18, particularlywhen the treatment in zone 10 is omitted as heretofore mentioned, is tobring the fuel into intimate contact with an aqueous solution of ametal-passivating salt of sodium. For the purpose of illustration, it isassumed that the alcohol is removed by a solution of sodium nitriteintroduced into zone 13 by means of line 20 and withdrawn as an aqueousalcoholic solution by means of line 21. It is to be understood that anynumber and arrangement of zones may be employed with respect to theprocess described. For instance, the operations of treating with alcoholand of separating from alcohol may, if desired, be carried outconsecutively, or even continuously, in a single vessel, although theillustrations show the treating and the separating in separate zones forpurposes of clarity. It is also to be understood that any suitable meansfor securing better mixing and contact likewise may be used.

The process of the present invention may be more fully understood by thefollowing examples.

EXAMPLE I A gasoline containing more than 50% cracked naphtha, having avapor pressure of about 11 lbs. per sq. in. at 100 F., and showing about60% distilled at 212 F. by ASTM test method D86 and a final boilingpoint of about 380 F, was mixed with 5% or" isopropanol and agitated at80 F. in the presence of air. The gum content of the gasoline blend wasdetermined initially and at various intervals of time during a testlasting 16 hours.

The gum content was determined by the General Motors method, which iscarried out in the manner described in AST M method D-381-50 but at atemperature of about 375 F. The method is intended to measureexistentgum; but, of course, some gum is inevitably formed by 4polymerization and oxidation of unsaturated hydrocarbone while the testis in progress, so that a slight decrease in General Motors gum afterthe treatment with alcohol is indicative of a decrease in the potentialgumforming tendency of the gasoline being treated. The test results wereas follows:

Time Elapsed From Start of Test, Hrs.

PZ-NNWPPQP P moomoooooommmo Thus, it is apparent that if a petroleum oilboiling in the range of motor'gamline is treated with an alcohol a roomtemperature in the presence of air, an improvement in the gum content ofthe fuel is obtained after the treatment has. progressed for asufficient length of time. In the absence of alcohol, the elfect of airwould be to increase the gmm content of the fuel according to Well-knownoxidation and polymerization phenomena.

EXAMPLE II Four one-gallon samples of a gasoline having thecharacteristics described in Example I were subjected to comparativetests. Two of the samples were duplicate control samples. The other twowere treated with 2% by volume of isopropanol and represented duplicatetest samples. The four samples were stored in bright iron cans offivegallon capacity and the cans were fitted with air-vents. The storagelasted 200' days and the samples were tested at intervals-for gumcontent as described in Example I and for peroxide number by a method inwhich ferrous sulfate is oxidized to. ferric sulfate and the amount offerric sulfate formed is measured by titration with titanous chloride.The results of the tests are summarized as follows:

Averages of duplicate tests of gasoline stored with and without-2% ofisopropanol without agitation, the treatment of gasoline with alcohol atambient temperatures in the presence of air is effective in retardingthe formation of gum. and of peroxides which are well-known in theart tobe associated with the formation of 81 ins s line.

EXAMPLE III A sample of gasoline having the same generalcharacteristics'as shown in Example I was tested for Copper Dish Gum bybeing evaporated from a dish of polished copper on a steam bath. Thetest is an approximate measure of potential gum-forming characteristicsof gasoline; because the copper metal acts catalytically to promote gumformation during the evaporation of the sample from the heated dish. Forcomparative purposes the test was repeated with various volumepercentages of isopropanol in the gasoline. In another comparable seriesof tests, corresponding volume percentages of acetone were blended inthe gasoline. The following results were obtained:

Copper Dish Gum, mgs./10O m1.

Vol. Percent Added Isopropanol- 117 62 60 81 100 Acetone-.- 117 58 50 5380 From the foregoing it is evident that for this gasoline under theconditions of the copper dish gum test there is an optimum percentage ofreagent at about 2% by volume. In this test acetone is even moreefiective than isopropanol from which it can be formed by catalyticoxidation. It is possible that the efiectiveness of the alcohol is duein part to its being oxidized; but the possibility is merelyconjectural.

EXAMPLE IV For illustrating the efiect of treating withmetalpassivators, a sample of heating oil was selected. It was a blendconsisting of about 25% catalytically cracked gas oil, 45% thermallycracked gas oil and 30% virgin gas oil and it had the following typicalcharacteristics:

Gravity, degrees API 34.1 Color (Tag Robinson Colorimeter) 11%Pensky-Marten flash-point, F. 158 Percent sulfur content 0.6Aniline-point, F. 130 ASTM distillation:

Initial boiling point, F. 342

50% off at F. 484

Final boiling point, F. 628

Four portions of the above heating oil were treated separately, eachwith an equal volume of an aqueous solution of a metal-passivatingsodium salt. The aqueous solutions were separated from the treated oilin each instance and the oil was tested for its tendency to form sludgein accelerated sediment-forming tests and also for the tendency for ironto become rusted when immersed in the water-saturated oil. Theaccelerated tests were run at 212 F. in air and in a closed containerunder oxygen pressure. Comparative results were as follows:

109; io z Treating agent None Sodiiinn Sodnim ag??? phate Nitritel\itrite mate Accelerated Sedimerit:

I|Ilg./1UU ml.,in 4 1 i 3 2 3.

air. IHESJIOO 1111.,in 32 30 31 11.

oxygen. Busting tendency, Heavy Light.-. Trace.-- None Medium.

12 days.

The samples of treated oil showed improved stability against theformation of sediment even under very severely accelerated oxidation andimproved anti-rusting characteristics.

EXAMPLE V For illustrating the effect of treating with various alcoholsand related materials, samples of the same heating oil as described inExample IV were treated with the reagents in various concentrations. Thesediment initially removable from the oil by filtration was measured, as

well as the accelerated sediment subsequently formed by heating in air.Comparative results were as follows:

effective to some degree in improving the stability of the heating oil.Pyrogallol and catechol have anti-oxidant properties, but the otherreagents have not. Consequently, the results must be interpreted asindicating an effect distinct from the inhibition of oxidation.

EXAMPLE V1 For illustrating the efiect of removing the volatile andwater-soluble alcohols from the treated fuels, samples of the sameheating oil as described in Example IV were treated with isopropanol,which was separated from them, after the treatment, in various ways.Comparative results were as follows:

Heating Oil Treated with Sediment, Mgs./l00 P ensky- Isopropanol ml.Marten gashoint,

2532; Method of Removal Filterable g i F.

0 0.5 4 158 0.5 0.2 1 106 0 0.1 2 158 0.5 Distilled to 365 F. 0.8 1 1765.0 None 0.3 1 5.0 Water-washing 0.2 2 158 5.0 Distilled to 365 F-.. 0.91 166 The lowering of the flash-point of the fuel by the volatilealcohol may be objectionable as an increased fire hazard. Therefore, itis desirable to remove the alcohol, except possibly in winter and inplaces where the fuel is normally stored in the presence of water. Thesedimentforming tendency of the fuel is improved still further when thealcohol is removed by distillation.

EXAMPLE VII Heating oil samples having properties as described inExample IV were treated with both isopropanol and an aqueous solution ofsodium nitrite in 10% concentration. In one test the treatment withalcohol was followed by the treatment with nitrite and in the other testthe order of treatments was reversed. The results of the tests were asfollows:

0.5 V01. 10% NaNOz and 002 Vol. l-C3H7QH 0.02 Vol. i-CaH7OH and 0.5 Vol.10% NaNOz Treatment per Vol None Sediment Tests:

Initially Filterable Acceld in Air Acceld in oxygen 32 5 BustingTendency, 12 Days- Heavy- None It is evident from the data thattreatment with sodium nitrite followed by treatment with isopropanol issuperior to treating with isopropanol alone as in Example V. It is alsoevident that treatment with isopi'opariol followed by treatment withsodium nitrite for removal of the isopropanol is superior :to thetreatments .shown in Example VI.

The present invention is thus broadly concerned with the treatment ofliquid fuels with alcohols and with the removal of volatile orwater-soluble alcohols from the treated fuels in order to improve thequality of the fuels, which are distillates like gasolines or heatingoils. The alcohols, when not wanted in the treated fuels, can be removedby distillation or preferably by washing with an aqueous solution of ametal passivator. Preferred modifications of the present invention areto improve the stability of heating oils against formation of sedimentby treating them with an alcohol and removing the alcohol with sodiumnitrite. The treated fuels maybe used without further treatment. Theymay be suitably blended with other fuels as desired. Suitableadditionagents may be incorporated in the treated fuels for further improvementof quality. Such addition agents may be antioxidants. In gasoline fuelstetraethyl lead and lead scavenging agents can be used advantageouslyafter the treatment according to the present invention. In diesel fuels,ignition promoters, for example alkyl nitrates, can be used after thetreatments of this invention. In heating oils, suitable additives foruse after the fuels have been treated in accordance with the presentinvention include sludge dispersers, detergents, antioxidants,pour-point depressors and rust-Preventives. Examples of additives withrustpreventive properties are lecithin, oil-soluble petroleum sulfonatesof sodium or calcium, and fatty acid esters of polyhydric alcohols, forexample sorbitan mono-oleate. For instance, the addition of 0.9%isopropanol and 1.0% sorbitan mono-oleate to the heating oil describedin EX- ample IV decreased the accelerated sediment from 4 mgs. to 0.3per 100 ml. and completely prevented the rusting of iron for 12 days incontact with the treated oil.

What is claimed is:

l. The process for the production of an improved liquid hydrocarbon fueloil of improved corrosion characteristics and increased stabilitycomprising the steps of introducing a liquid hydrocarbon fuel containingat least cracked gas oil and boiling in the range below about 700 F.into an initial treating zone, contacting said fuel in said zone with atreating agent consisting essentially of from about 0.5% to about byvolume of isopropanol based on the volume of said fuel while maintainingthe temperature in said treating zone in the range of about 100 F. toabout 180 F., passing the resulting mixture to a second treating zone,contacting said resulting mixture in said second treating zone with anaqueous solution of a water-soluble metal-,passivating alkali metal saltselected from the group consisting of nit'rites, nitrates, chromates,bichromates, phosphates, phosphites, borates and :benzoates to extractthe isopropanol from said mixture, and separating improved hydrocarbonfuel from the resulting aqueous solution of water-solublemetal-passivating alkali metal salt and isopropanol.

2. The process according to claim 1 in which said metal-passivatingalkali metal salt is sodium nitrite.

3. The process according to claim 1 in which the volume of said treatingagent is from about 1% to about 5% based on the volume of said fuel, andin which said metal-passivating alkali metal salt -is sodium nitrite.

4. The process for the production of an improved hydrocarbon fuel oil ofimproved corrosion'characteristics and increased stability comprisingthe steps of introducing a liquid hydrocarbon fuel containing at leastabout 10% cracked gas oil-and boiling in the range below about 700 E.into an initial treating zone, contacting said fuel with an aqueoussolution of sodium nitrite, passing the resulting mixture to a secondtreating zone, contacting said mixture in said zone with a secondtreating agent consisting essentially of from about 1% to about 5% byvolume of isopropanol based on the volume of said fuel while maintainingthe temperature in said second treating zone in the range of about F. toabout 180 F., passing the resulting mixture to a third treating zone,contacting this resulting mixture in said third treating zone with afurther portion of aqueous solution of sodium nitrite to extract theisopropanol from said mixture, and separating improved hydrocarbon fuelfrom the resulting aqueous solution of sodium nitrite and isopropanol.

References Cited in the file of this patent UNITED STATES PATENTS 66,364Loomis et al July 2, 1867 685,895 Wirth Nov. 5, 1901 1,256,537 Dyer etal Feb. 19, 1918 1,791,521 Bjeregaard Feb. 10, 1931 1,822,351 Krauch etal Sept. 8, 1931 1,899,042 Malisoff r Feb. 28, 1933 1,960,974 Krauch etal May 29, 1934 1,968,842 Malisoif Aug. 7, 1934 2,309,653 Leum et alFeb. 2, 1943 FOREIGN PATENTS 169,573 Great Britain Oct. 6, 1921

1. THE PROCESS FOR THE PRODUCTION OF AN IMPROVED LIQUID HYDROCARBON FUELOIL OF IMPROVED CORROSION CHARACTERISTICS AND INCREASED STABILITYCOMPRISING THE STEPS OF INTRODUCING A LIQUID HYDROCARBON FUEL CONTAININGAT LEAST 10% CRACKED GAS OIL AND BOILING IN THE RANGE BELOW ABOUT 700*F. INTO AN INITIAL TREATING ZONE, CONTACTING SAID FUEL IN SAID ZONE WITHA TREATING AGENT CONSISTING ESSENTIALLY OF FROM ABOUT 0.5% TO ABOUT 20%BY VOLUME OF ISOPROPANOL BASED ON THE VOLUME OF SAID FUEL WHILEMAINTAINING THE TEMPERATURE IN SAID TREATING ZONE IN THE RANGE OF ABOUT100* F. TO ABOUT 180* F., PASSING THE RESULTING MIXTURE TO A SECONDTREATING ZONE, CONTACTING SAID RESULTING MIXTURE IN SAID SECOND TREATINGZONE WITH AN AQUEOUS SOLUTION OF A WATER-SOLUBLE METAL-PASSIVATINGALKALI METAL SALT SELECTED FROM THE GROUP CONSISTING OF NITRITES,NITRATES, CHROMATES, BICHROMATES, PHOSPHATES, PHOSPHITES, BORATES ANDBENZOATES TO EXTRACT THE ISOPROPANOL FROM SAID MIXTURE, AND SEPARATINGIMPROVED HYDROCARBON FUEL FROM THE RESULTING AQUEOUS SOLUTION OFWATER-SOLUBLE METAL-PASSIVATING ALKALI METAL SALT AND ISOPROPANOL.